Routines
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41786: Handler: Display Room Exits
Used by the routines at LoadTape, 43933 and ChangeRoom.
Handles displaying the exits available for the current room.
Handler_RoomExits 41786 PUSH IX Stash IX, HL, DE and BC on the stack.
41788 PUSH HL
41789 PUSH DE
41790 PUSH BC
41791 LD A,(48077) Jump to Handler_RoomExits_1 if *Count_RoomsWithImages is set to zero.
41794 OR A
41795 JR Z,Handler_RoomExits_1
The version of the game being played DOES have graphics, so continue.
41797 LD A,(41222) Fetch *CurrentRoom and load it into A.
41800 LD HL,48019 Fetch the address of the table from Table_RoomsWithImages.
41803 LD BC,(48077) Fetch the count of the number of rooms in the table from *Count_RoomsWithImages.
41807 CPIR Search to see if the current room ID is in the table.
41809 JR NZ,Handler_RoomExits_1 Jump to Handler_RoomExits_1 if the current room ID does not appear in the table.
The current room does have an image associated with it.
41811 LD A,(48077) Calculate the index of the current room in the table.
41814 INC C
41815 SUB C
41816 LD B,A
41817 XOR A A=0.
41818 OR E Set the bits from E.
41819 JR NZ,Handler_RoomExits_0 Jump to Handler_RoomExits_0 if C is not equal to E.
41821 LD HL,41128 HL=41128.
41824 LD A,B A=B.
41825 CALL 41396 Call 41396.
41828 LD C,A C=A.
41829 AND (HL) Merge the bits from *HL.
41830 JR NZ,Handler_RoomExits_1 Jump to Handler_RoomExits_1 if C is not equal to *HL.
41832 LD A,(HL) A=*HL.
41833 OR C Set the bits from C.
41834 LD (HL),A Write A to *HL.
Handler_RoomExits_0 41835 CALL ClearLines Call ClearLines.
41838 LD HL,48038 HL=48038.
41841 LD E,B E=B.
41842 LD D,0 D=0.
41844 ADD HL,DE HL+=DE.
41845 LD A,(HL) A=*HL.
41846 CALL Handler_Images Call Handler_Images.
Handler_RoomExits_1 41849 CALL ClearLines Call ClearLines.
41852 CALL SetDefaultScreenPosition Call SetDefaultScreenPosition.
41855 CALL 42031 Call 42031.
41858 CALL GetRoomPointer Call GetRoomPointer.
41861 LD D,H Store this in DE for later.
41862 LD E,L
Count the number of exits in the room data.
41863 LD B,6 Set an "exits" counter in B of 6.
41865 LD C,0 Initialise C to 0 to count the number of valid exits.
41867 XOR A Set A to 0 which is used just for the comparison.
RoomExitsCount_Loop 41868 CP (HL) Does this room have an exit?
41869 JR Z,RoomExitsCount_Skip Jump to RoomExitsCount_Skip if this room doesn't have an exit for this position.
41871 INC C Increment the valid exits count by one.
RoomExitsCount_Skip 41872 INC HL Move to the next byte of room data.
41873 DJNZ RoomExitsCount_Loop Decrease the exits counter by one and loop back to RoomExitsCount_Loop until all the exits have been checked.
Process the exits count result.
41875 OR C Jump to RoomExits_YouCanSee if no exits were found
41876 JR Z,RoomExits_YouCanSee
41878 LD A,C Jump to RoomMultipleExits if more than 1 exit was found.
41879 CP 1
41881 JR NZ,RoomMultipleExits
Only one exit was found:
Print " There is an exit ".
41883 LD HL,7 HL=Messaging_ThereIsAnExit.
41886 CALL PrintCompressedString Call PrintCompressedString.
41889 LD H,D Retrieve the room data pointer and load it into HL.
41890 LD L,E
41891 LD IX,41289 Set a pointer in IX to Table_Directions.
41895 XOR A Set A to 0 which is used just for the comparison.
41896 JR RoomCheckForExit Jump to RoomCheckForExit.
Move both the pointers to the next item of data (increment by two for the direction name table pointer as it contains addresses).
RoomCheckForExit_Loop 41898 INC HL Move to the next byte of room data.
41899 INC IX Increment the direction name table pointer by two.
41901 INC IX
RoomCheckForExit 41903 CP (HL) Jump to RoomCheckForExit_Loop if the current exit isn't a valid exit.
41904 JR Z,RoomCheckForExit_Loop
41906 LD L,(IX+0) Get the direction name from the direction name table.
41909 LD H,(IX+1)
41912 CALL PrintCompressedString Call PrintCompressedString to print the direction name.
41915 JR RoomExits_PrintFullStop Jump to RoomExits_PrintFullStop.
More than one exit was found:
Print " There are exits:-".
RoomMultipleExits 41917 LD HL,6 HL=Messaging_ThereAreExits.
41920 CALL PrintCompressedStringAndNewline Call PrintCompressedStringAndNewline.
41923 LD H,D Retrieve the room data pointer and load it into HL.
41924 LD L,E
41925 LD IX,41289 Set a pointer in IX to Table_Directions.
41929 XOR A Set A to 0 which is used just for the comparison.
41930 JR RoomCheckForExits Jump to RoomCheckForExits.
So as not to corrupt the pointer to the room data (as HL is also used when printing), it's temporarily held in DE.
RoomExits_Initialise 41932 EX DE,HL Switch back the DE and HL registers.
RoomCheckForExits_Loop 41933 INC HL Move to the next byte of room data.
41934 INC IX Increment the direction name table pointer by two.
41936 INC IX
RoomCheckForExits 41938 CP (HL) Jump to RoomCheckForExits_Loop if the current exit isn't a valid exit.
41939 JR Z,RoomCheckForExits_Loop
41941 EX DE,HL Temporarily store the room data pointer in DE.
41942 LD L,(IX+0) Get the direction name from the direction name table.
41945 LD H,(IX+1)
41948 CALL PrintCompressedString Call PrintCompressedString to print the direction name.
41951 DEC C Decrease the valid exits count by one.
41952 LD A,C Jump to RoomExits_PrintFullStop if there are no more exits to process.
41953 CP 1
41955 JR C,RoomExits_PrintFullStop
41957 JR Z,RoomExits_PrintAmpersand Jump to RoomExits_PrintAmpersand if there is only one exit left to process.
Print a comma character: ",".
41959 LD A,44 A=44.
41961 CALL PrintCharacter Call PrintCharacter.
41964 XOR A Reset A back to 0 for the comparison.
41965 JR RoomExits_Initialise Jump to RoomExits_Initialise to continue processing.
Print " & ".
RoomExits_PrintAmpersand 41967 LD HL,5 HL=Messaging_Ampersand.
41970 CALL PrintCompressedString Call PrintCompressedString.
41973 XOR A A=0.
41974 JR RoomExits_Initialise Jump to RoomExits_Initialise.
Print ".".
RoomExits_PrintFullStop 41976 LD A,46 A=46.
41978 CALL PrintCharacter Call PrintCharacter.
Print a newline.
41981 LD A,13 A=13.
41983 CALL PrintCharacter Call PrintCharacter.
Are there any objects here?
RoomExits_YouCanSee 41986 LD A,(41222) A=*CurrentRoom.
41989 CALL CheckRoomObjects Call CheckRoomObjects.
41992 JR NZ,RoomExits_Return Jump to RoomExits_Return if no objects were found at this location.
Print " You can see:-".
41994 LD HL,4 HL=Messaging_YouCanSee.
41997 CALL PrintCompressedStringAndNewline Call PrintCompressedStringAndNewline.
Print the objects at this location.
42000 LD A,(41222) A=*CurrentRoom.
42003 CALL PrintObjects Call PrintObjects.
RoomExits_Return 42006 POP BC Restore BC, DE, HL and IX from the stack.
42007 POP DE
42008 POP HL
42009 POP IX
42011 RET Return.
View the equivalent code in;
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